Computational study of the pressure-driven flow in a four-electrode rectangular micro-electrochemical accelerometer with an infinite aspect ratio

Numerical simulation is done on the pressure-driven flow in a four-electrode rectangular micro-electrochemical accelerometer with an infinite aspect ratio. The pressure gradient is proportional to the applied acceleration. Two kinds of electrode arrangements along the channel, the anode–cathode–cathode–anode (ACCA) and the cathode–anode–anode–cathode (CAAC) layouts, are studied. With the imposed electric potential difference between the electrodes, the electrode reaction, I3−+2e−⇌3I−, occurs at the cathodes, with the reverse reaction occurring simultaneously at the anodes. For the given electrolyte, it is found that the cathodic current difference is two-order-of-magnitude larger than the anodic current difference and thus employed as the output electric current. The magnitude of the output electric current is found to be non-monotonous as the pressure gradient: when the pressure gradient is lower than the critical pressure gradient corresponding to the peak output electric current, the output electric current monotonously increases as the pressure gradient; when the pressure gradient is larger than the critical pressure gradient, the output electric current decreases as the pressure gradient and asymptotically approaches zero. The critical pressure gradient is found to be slightly larger for the ACCA layout. Due to the higher tri-iodide concentration compared to that found in the ACCA layout, when the pressure gradient is below the critical pressure gradients of both kinds of layouts, the CAAC layout generates larger output electric current.